In order to increase user high data flow and system throughput, 3GPP R5 standard protocol introduces a High Speed Downlink Shared Channel (HS-DSCH), the physical channel mapped by the channel applies time division and code division, and the channel applies the technology of Hybrid Automatic Repeat reQuest (HARQ) and Adaptive Modulation and Coding (AMC) to make the peak rate reach to 10.8 Mbps˜30 Mbps. Its ultimate target is to increase the system capacity and reduce transmission delay so as to meet the subscribers' requirement for Quality of Service (QoS) by providing access to the High Speed Packet Service.
3GPP protocol standard strengthens Forward Access State (CELL_FACH) in connection mode of Radio Resource Control (RRC), and/or Paging State (CELL_PCH/URA_PCH) in connection mode of Radio Resource Control (RRC), that is, High Speed Downlink Packet Access (HSDPA) technology can also be used in CELL_FACH and/or CELL_PCH/URA_PCH, and herein using the High Speed Shared Packet Access (HSDPA) technology in the state of CELL_FACH and/or CELL_PCH/URA_PCH is called as enhanced common state of fortified connection mode for short. When user equipment is in the enhanced common state of fortified connection mode, data in logical channels including Common Control Logical CHannel (CCCH), Dedicated Control Logical CHannel (DCCH), Dedicated Traffic Logical CHannel (DTCH), Multimedia Control Logical CHannel (MCCH), Multimedia Traffic Logical CHannel (MTCH) and so on can be mapped to the High Speed Downlink Shared Channel to be transmitted.
However, since the base station implements data scheduling, in order to avoid data overflow during the radio network controller transmitting data to the base station, flow control should be performed between base station and radio network controller, that is, the radio network controller could apply the base station for the cache amount of data to be transmitted, while the base station could allocate data capacity to the radio network controller. At present, the capacity allocated to the radio network controller by the base station in 3GPP standard is indicated by Maximum MAC-d PDU Length (maximum length of Protocol Data Unit of Media Access Control entity) and HS-DSCH Credits (the number of PDUs with Maximum Mac-d PDU Length that could be transmitted during one time interval of High Speed Downlink Shared Channel (HS-DSCH Interval)).
For the use of High Speed Downlink Shared Channel in enhanced common state of fortified connection mode, there is no specification on how to implement flow control between the radio network controller and the base station in prior art, thus the user equipment in enhanced common state of fortified connection mode cannot receive data accurately; therefore, there is a need for re-indicating the capacity allocated to the radio network controller by the base station, so as to ensure that the radio network controller and base station can also implement flow control regarding the user equipment in enhanced common state of fortified connection mode.